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Menstruation doesn't greatly affect asthma

By Anne Harding

NEW YORK (Reuters Health) - Women with asthma are not at greatly increased risk of having an asthma attack or visiting the emergency department (ED) for asthma care immediately before and during menstrual bleeding, researchers report in the medical journal Thorax.

Dr. Barry E. Brenner of the University of Arkansas for Medical Sciences in Little Rock and colleagues found that women seen at the ED with asthma were slightly more likely to be in the preovulatory phase or the phase just before or during their menstrual flow (perimenstrual phase). The findings were the same when the researchers classified the women by date of symptom onset.

This issue of perimenstrual exacerbation of asthma, which has wound up even migrating into some textbooks, has been refuted, Brenner told Reuters Health. However, he added, there may be a subset of women for whom menstrual phase does indeed play a role in asthma severity.

Both asthma in general and ED treatment for acute asthma exacerbations are more common among boys than girls, but increase in females during adulthood, Dr. Brenner and his team note.

This suggests reproductive hormones may somehow be involved in the course of asthma, and a number of researchers have suggested that certain phases of the menstrual cycle could trigger asthma exacerbation.

Two previous studies found this was the case, but had conflicting results. One identified a sharp increase in asthma admissions during the premenstrual phase, while the other found admission was more likely before ovulation.

To investigate further, the team enrolled 792 women who were seen at the ED for an acute asthma exacerbation, and then classified them by their menstrual phase at the date of symptom onset and the date of hospital admission.

Based on date of symptom onset, 28 percent of the women were preovulatory, 21 percent were ovulating, 21 percent were post-ovulatory and 27 percent were perimenstrual. Based on ED visit date, the corresponding percentages were almost identical.

Thus, the researchers note that there is no marked increase in exacerbations during the perimenstrual phase. However, they add that the perimenstrual and preovulatory phases of the menstrual cycle may impact asthma severity in some women.

These phases, they conclude, "could be actual triggers of an asthma exacerbation or they might serve as 'co-factors' that worsen other recognized triggers of acute asthma."

SOURCE: Thorax, October 2005.

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